Iranian nuclear scientist, Shahram Amiri, who claimed to have been abducted by CIA agents, arrived back in Iran's capital, Tehran, early Thursday morning.
Amiri's disappearance a year ago resulted in conflicting accounts of his whereabouts by Iranian and U.S. officials.
On Monday, Amiri surfaced in the Pakistan Embassy in Washington.
The U.S. State Department says that Amiri had been in the United States of his own free will and was free to go at any time.
Amiri was an employee of Iran’s Malek Ashtar University, which has links to Iran’s Islamic Revolutionary Guards, according to the Council on Foreign Relations.
After his arrival in Iran's capital on Thursday morning, Amiri spoke to a select group of journalist given permission to cover his return, according to the Associated Press.
Amiri repeated his previous claims that he was abducted a year ago while on the Hajj pilgrimage in Saudi Arabia.